Part 2 (Resistance Unbalance Tolerances)
Another very good change to the AR-100 is the addition of resistance unbalance limits for random and form wound coils. For over thirty years PdMA has been preaching the importance of resistive imbalance as an indicator of Power Circuit health and now we are excited to reference another well respected standard in support of it. In addition the AR-100 appears to have adopted the same calculation as PdMA for the resistance unbalance value, which is the largest deviation from the average. The newly added AR-100 limit for resistance unbalance is 2% for random wound coils and 1% for form wound coils. There is a little bit of wiggle room for concentric wound stator windings to exceed 2%. These values would be based on testing from the motor only and not inclusive of the starter contacts or power cables.
To view case studies on power circuit integrity visit the PdMA YouTube Channel at https://www.youtube.com/channel/UC-cUONWaudkKReNwC0PPXMQ/featured.